Wound closure and drainage system

ABSTRACT

A vacuum system for draining an open wound from liquids exuded therefrom, comprising an enclosure sealable to the wound circumference, a vacuum pump including a disposable pump unit detachably attachable to a non-disposable drive unit, and a waste container for collection of drained liquids. The enclosure has an outlet connected by means of a tube to an inlet of the pump unit and the waste container is connected to an outlet of the pump unit, such that when the vacuum pump is operated the drained liquids flow through the vacuum pump. The enclosure has one or more bleeding holes provided therethrough or adjacent to its outlet so that ambient air may enter the tube and flow together with the drained liquids. The enclosure and the waste container are disposable so that the drained liquids contact only disposable elements and may be disposed of together with all disposable elements.

FIELD OF THE INVENTION

This invention relates generally to wound healing, and more specificallyto healing of wounds by negative pressure drainage.

BACKGROUND OF THE INVENTION

Negative pressure applied to a wound enhances drainage of fluids orexudate from the wound and promotes tissue growth and wound healing.This method of healing (known as “cupping”) was exercised since thetimes of ancient Greek physicians until the 19th century.

WO 96/05873 describes a therapeutic apparatus for stimulating healing ofwounds. The apparatus comprises a porous foamed pad which is sealed onthe wound and connected by a tube to an inlet of a canister. A vacuumpump is connected to an outlet of the canister. A bacterial filterpositioned over the outlet of the canister protects the vacuum pump fromcontamination by wound drainage fluids sucked into the canister. Thepump, the canister and control circuitry are disposed in a case.

WO 97/18007 discloses a portable wound treatment apparatus using asimilar arrangement of a porous pad, canister and vacuum pump. Thecanister and the pump are in one housing which accommodates also thecontrol circuitry and is wearable on a harness or a belt.

U.S. Pat. No. 6,648,862 describes a portable vacuum desiccator using asimilar arrangement as above, the canister being formed as a cartridgecontaining a trapping agent (desiccator). The vacuum pump and thecanister may be integrated and detachable from the pump motor andcircuitry.

Current negative pressure wound drainage systems such as the onesdescribed above suffer from the following deficiencies:

Since the negative pressure applied to the wound area is created by pumpsuction, the flow into the pump is likely to contaminate the pump, orconversely, to require costly and complex methods of isolating the pumpfrom the wound exudate such as antibacterial filters.

The wound exudate is collected in a rigid canister, which must be largeenough to prevent it from overflowing, and thus it is bulky and aninconvenient burden for ambulatory patients, who carry a portable systemwith them.

Conventional wound drainage systems utilize an air tight seal of thewound, which is helpful in obtaining and maintaining negative pressure,but requires a pressure relief or bleed valve to produce the pressurecycling desirable to obtain accelerated wound closure, as described inWO 96/05873.

A sealed wound dressing or enclosure, when under negative pressure, willpromote migration of the exudate toward the negative pressure source,through the connecting tube, which may occlude, should the exudatecoagulate.

The need to monitor and control the negative pressure level inconventional systems requires the use of a vacuum transducer, gage orrelief valve, which must be connected to the suction tube, which issubject to contamination. Cleaning, disinfecting or isolating thenegative pressure monitoring or controlling device are complex, costlyand un-reliable.

SUMMARY OF THE INVENTION

It is the purpose of this invention to alleviate all the above listeddeficiencies, by providing a wound drainage enclosure and vacuum system,which are impervious to contamination and easy to use.

In accordance with a first aspect of the present invention, there isprovided an enclosure for draining an open wound from liquids exudedtherefrom. The enclosure is attachable to the wound circumference so asto define a confined volume, and has an outlet, for example formed as anipple, connectable by means of a tube to an inlet of a vacuum pump sothat negative pressure may be created in said confined volume. One ormore bleeding holes are provided in the enclosure or adjacent to itsoutlet such that ambient air can enter the tube and flow together withthe exuded liquids when negative pressure is present. Ambient pressuremay be restored in the confined volume when the vacuum pump is notoperating.

The bleeding hole in the enclosure may be a calibrated orifice or otherflow restrictors providing for controlled flow of ambient air into theenclosure or into its outlet. For instance, a hole plugged with opencell foam or an open pore sintered metal plug, which restrict the flow,but are not susceptible to plugging as is a small orifice.

The bleeding hole renders the wound closure vented or non-airtight, asdistinguishable from conventional wound closures. The flow of air fromthe bleeding hole in the wound closure, in response to the negativepressure created by the vacuum pump, facilitates the removal of exudate,which might otherwise coagulate, dry-up and occlude the tubing.

According to another aspect of the present invention, there is provideda method for draining an open wound from liquids exuded therefrom. Themethod includes:

providing an enclosure and sealing it to the wound circumference so asto define a confined volume,

connecting the confined volume to a vacuum pump,

connecting a waste container for collection of drained liquids to thevacuum pump, and

operating said vacuum pump to draw the exuded liquids from the wound.

The method is characterized in that the confined volume is connected toan inlet of the vacuum pump and the waste container is connected to anoutlet of the vacuum pump such that the drained liquids flow throughsaid vacuum pump.

The method may include employment of an enclosure with bleeding orificesso that ambient air is allowed to enter the tube and flow together withthe drained exuded liquids.

Preferably, gases are separated and released from the drained exudedliquids.

According to a further aspect of the present invention, there isprovided a vacuum system for practicing the above method. The vacuumsystem may use a totally disposable vacuum pump, together with a wastecollection bag, as disclosed in WO03016719. The vacuum pump is atwo-chambered diaphragm pump adapted for pumping gases and liquidsand/or any combination thereof. The vacuum pump is capable of pumpingair and fluid which enter its inlet port, to a waste bag attached to itsoutlet port. The waste bag is vented to the atmosphere, such that itcollects only the fluids which enter it.

The vacuum system may be adapted to be carried by an ambulatory patient.

According with a next aspect of the present invention, there is provideda disposable assembly for draining an open wound from liquids exudedtherefrom. The assembly comprises an enclosure attachable to the woundcircumference so as to define a confined volume, a vacuum pump unitconnected to the enclosure so that negative pressure may be created inthe confined volume, and a waste container connected to the vacuum pumpunit. The vacuum pump unit has means for detachably attaching to a driveunit for operating the pump unit. The enclosure is connected to an inletof the vacuum pump unit and the waste container is connected to anoutlet of the vacuum pump unit, such that when the vacuum pump unit isoperated the drained liquids flow therethrough.

Preferably, the pump unit and the drive unit are adapted for attachingand detaching by simple hand manipulations.

The enclosure may have bleeding holes as described above.

The vacuum pump unit is preferably a two-chambered diaphragm pumpadapted for pumping gases and liquids and/or any combination thereof.

The waste container may contain a porous media adapted to soak up thedrained liquids and may be in the form of a collapsible or foldable bag.

The drained liquids and air contact only the parts of the disposableassembly. The drained exuded liquids may then be disposed of togetherwith the disposable assembly. More specifically, the pump unit isdisposed of after use, together with the tubing connected to it, as wellas the waste bag connected, with its content, and with the wound closurewhich may be connected to the pump unit via the tube.

In accordance with yet another aspect of the present invention, there isprovided a vacuum system as described above where the vacuum pump has adrive unit and a control block adapted to power the drive unit so that apredetermined level of negative pressure is maintained in the confinedvolume. The control block has a sensor for sensing working parameters ofthe drive unit and means for deriving the level of negative pressure inthe confined volume from these working parameters, in order to maintainsaid predetermined level. The sensor has no fluid connection with theconfined volume.

For example, the drive unit may comprise a direct current electric motorand the sensor may sense the electric current driving the motor. Thesame function of negative pressure control may be accomplished by anadjustable torque limiting clutch, placed between the motor output shaftand the pump.

The control block may be provided with alarm means to warn the user ifthe predetermined level of negative pressure is not maintained.

If the vacuum pump comprises a disposable pump unit and the drive unitis detachably attachable to the pump unit, the control block withmonitoring means is preferably associated with the drive unit which isnon-disposable.

Thus, indirect means are provided for controlling or monitoring thelevel of negative pressure applied to the wound, without making anydirect connection to a vacuum sensor, transducer or gage to any portionof the system, which has the negative pressure applied to it. Theindirect negative pressure monitoring and control result from the needto dispose of any portion of the system, which may come in contact withthe pumped media, which is likely to be contaminated or infectious.Accordingly, all the disposable components in the system may berelatively low in cost, to promote discarding them after use. Pressuretransducers, vacuum gages or sensors, are relatively costly, and thusnot considered disposable.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be applied, apreferred embodiment will now be described, by way of non-limitingexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic sectional view of the vacuum system of the presentinvention applied on a wound.

FIG. 2 shows the disposable portion of the system of FIG. 1.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention provides a system and a method of treating andhealing of a body wound, by applying a negative pressure to the wound,over an area sufficient to promote migration of epithelial andsubcutaneous tissue toward the wound.

It is appreciated that the detailed description that follows is intendedonly to illustrate certain preferred embodiments of the presentinvention. It is in no way intended to limit the scope of the invention,as set out in the claims.

With reference to FIG. 1, in accordance with the present invention, avacuum system 10 for draining an open wound from liquids exudedtherefrom comprises a wound enclosure 12, a vacuum pump 14, and wastecollection bag 31. The wound enclosure 12 is connected by a suction tube16 to an inlet 11 of the vacuum pump. The waste collection bag 31 isconnected to an outlet 22 of the vacuum pump. Thereby, when the vacuumpump 14 is operated, the drained liquids flow through the pump into thewaste bag 31.

Suction tube 16 is connected to nipple 38 of the enclosure 12 whichcovers wound area of the body 34 such that suction of air through tube16 creates negative pressure in the volume above the wound area of thebody 34. A bleeding orifice 35 is provided within the enclosure 12, oradjacent to it as a tube orifice 37, allowing ambient air to flow intoand through suction tube 16, rendering enclosure 12 non-air tight, orvented. This feature, unlike conventional sealed closures, provides forquick movement of exudate entering suction tube 16, toward the vacuumpump 14, and into the waste bag 31, before it dries up or coagulates andoccludes the tube. This feature also provides for introduction ofambient pressure to the wound area of the body 34 whenever the vacuumpump stops pumping, allowing cyclic negative pressure application to thewound, by cycling the vacuum pump on and off alternately.

Instead of the bleeding orifice 35 in the enclosure, other flowrestrictors may be used to provide for controlled flow of ambient airinto the enclosure or into the outlet. For instance, a hole plugged withopen cell foam or an open pore sintered metal plug, which restrict theflow, but are not susceptible to plugging as is a small orifice.

The vacuum pump 14 comprises a pump unit 18 and a drive unit 40 whichare detachably attachable to each other, as explained below. The pumpunit 18 includes a two-chambered housing 17 and a diaphragm 24 securedto the underside of the two-chambered housing 17 so as to form a workingchamber 29.

The two-chambered housing 17 has a first chamber 13 with the inlet 11and a second chamber 21 with an outlet 22. The suction tube 16 isconnected to the inlet 11. Two one-way valves 19 and 20 are present atthe bottom of the first chamber 13 and the second chamber 21,respectively. To the bottom of the two-chambered housing 17 there isattached a mounting base 23, used to mount the housing 17 to the driveunit 40 by means of a bayonet lock.

The diaphragm 24 has an integral rod-shaped drive member 25, which isused for engagement with the drive unit 40.

The drive unit 40 includes an electric motor 39, batteries 41 and acontrol block 50 described below. The shaft of the motor 39 has a crank27 coupled to a reciprocating rod 26. The rod 26 has a receptacle with acavity adapted to receive and lock therein the drive member 25.

When the pump unit 18 is attached to the drive unit 40 by means of thebayonet lock in the base 23, the drive member 25 is received in thereceptacle cavity of the reciprocating rod 26 and then locked therein.

Upon activation of the motor 39, the crank 27 is rotated andreciprocates the receptacle rod 26, causing the diaphragm 24 to expandand contract the working chamber 29. Thus the pump unit 18 pumps air orliquid that passes through the one-way valves 19 and 20.

Air and liquids enter the two-chambered housing 17 through the inlet 11and suction tube 16 which is connected to the patient's wound enclosure12, for the removal of exudate. Liquids and air enter the first chamber13, which is under negative pressure when diaphragm 24 reciprocates,driving them past one-way valve 20, into the second chamber 21. The airand liquid which are pumped through outlet 22, enter waste bag 31.

The pump's ability to pump air and liquid, unlike conventional pumps,which are efficient in pumping only one type of matter, is enhanced bythe flexibility of the diaphragm 24 which allows the diaphragm to yieldwhen encountering heavy loads, such as those present when pumpingliquid. This diaphragm flexibility also provides an additionalsubstantial advantage: when the negative pressure in working chamber 29is high, the diaphragm 24 stretches to allow the reciprocation of thereceptacle rod 26 to occur, at minimal burden to the electric motor 39.

The waste bag 31 has a vent 15, through which air and gas are dischargedto the atmosphere. Accordingly, waste bag 31 will retain only the wastefluids which are pumped into it. The waste bag may contain a porousmedia 47 adapted to soak up the drained liquids.

It is important to note that waste bag 31 is made of thin plastic sheet,which allow it to be folded or collapsed when not full, providing theconvenience of having minimal bulk and minimal inconvenience to thepatient using or carrying it.

The drive unit 40 also includes a control block 50 with control circuitssuch as cycle control 42, which turns the motor pump on and offalternately, motor voltage and current monitoring and control 43, whichcontrols the negative pressure level produced by the pump unit 18, bycontrolling the voltage and current which drive motor 39. At any givenvoltage which drives motor 39, the current draw of the motor is directlyrelated to the negative pressure generated by the pump 18. Accordingly,monitoring of the current which the motor 39 draws allows for indirectmonitoring of the negative pressure attained by pump 18. The ability tomonitor the negative pressure developed by pump 18, indirectly,precludes the need of making an infectious negative pressure lineconnection to a pressure transducer or vacuum gage.

For example, if the motor 39 is a direct current electric motor, asensor may sense the electric current driving the motor. Since thedirect current motor output torque is directly related to the currentdriving the motor, and since the motor output torque is directly relatedto the negative pressure the pump 18 produces, monitoring the motorcurrent or controlling it, provide for monitoring and controlling thenegative pressure produced by the vacuum pump. Motor current monitoringis only one of the available methods of indirect negative pressuremonitoring and controlling. The same function of negative pressurecontrol may be accomplished by an adjustable torque limiting clutchplaced between the motor output shaft and the crank 27.

The control block 50 also has a negative pressure comparator 44, whichcompares the desired set negative pressure level obtained by pump 18,and the actual monitored negative pressure level as obtained indirectlyfrom motor voltage and current monitoring and control 43. Comparator 44will activate audible alarm 45, whenever pump 18 fails to reach thedesired pre-set negative pressure level.

FIG. 2 shows the disposable portion of the system as an assembly 60,which includes the pump unit 18, the waste bag 31, the connecting tube16 and the wound enclosure 12, all separated from the drive unit andfrom the wound area of the body 34. The assembly 60 may be disposed ofin its totality after use, and replaced by a new assembly, thus keepingthe costly drive unit 40 free from any contamination. It would beobvious to those skilled in the art, that the present inventionalleviates the need for cleaning or disinfecting any portion of driveunit 40 after use, or providing protective means, such as filters, tokeep contaminants from reaching the costly drive 40.

The invention claimed is:
 1. A method for applying negative pressure toa wound, the method comprising: (a) providing a vacuum system comprisingan enclosure, a venting arrangement, a tube, a vacuum source, and acontroller, wherein the enclosure is attachable to a periphery of thewound so as to define a confined volume, the enclosure has an enclosureoutlet connectable to said vacuum source via said tube so that negativepressure can be selectively created in said volume, the ventingarrangement comprises a flow restrictor to restrict flow through saidventing arrangement and to thereby provide a controlled flow of ambientair into said vacuum system upstream of the vacuum source, and thecontroller is configured for controlling operation of the vacuum sourcewhile providing venting of the vacuum system via said ventingarrangement; and (b) when the enclosure has been attached to a peripheryof the wound, operating the controller to control operation of thevacuum source while the vacuum system is being vented via the ventingarrangement to thereby provide a desired level of said negative pressurein said confined volume.
 2. The method according to claim 1, wherein thevacuum source comprises a vacuum pump driven by an electric motor, andwherein step (b) comprises controlling operation of said motor tothereby provide a desired level of said negative pressure in saidconfined volume.
 3. The method according to claim 2, wherein step (b)comprises controlling at least one of the electric current, or thevoltage, or the torque of said motor to control said level of saidnegative pressure in said confined volume.
 4. The method according toclaim 1, wherein said venting arrangement comprises at least one of: oneor more bleeding holes; a porous body; and an orifice.
 5. The methodaccording to claim 1, wherein said flow restrictor is provided in anyone of the enclosure or the tube.
 6. The method according to claim 1,wherein said venting arrangement is located outside said enclosure andcomprises a flow restrictor to restrict flow through said ventingarrangement and to thereby provide a controlled flow of ambient air intosaid tube, said controlled flow of ambient air entering said tube viasaid venting arrangement without entering said enclosure.
 7. The methodaccording to claim 1, comprising allowing ambient pressure to berestored in said confined volume via said venting arrangement when saidvacuum source is not operating.